Nanoporous silicon nitride membranes are fabricated by combining polystyrene colloidal lithography with Micro-Electro-Mechanical Systems, and then freestanding bilayer lipid membranes are constructed across the nanopores by the vesicle method. The topography and mechanical properties of the freestanding bilayer lipid membranes are investigated using the imaging and force curve modes of variable-temperature atomic force microscopy (AFM). The fluidity and self-repair of the freestanding bilayer lipid membranes are observed by AFM, which gives enough freestanding area for further investigations. Force curve measurements demonstrate that both breakthrough and adhesion forces decrease as the temperature increases; i.e., the mechanical stability of freestanding bilayer lipid membranes decreases as the temperature rises. The breakthrough force of freestanding bilayer lipid membranes is smaller than that of supported membranes. Moreover, the adhesion force of freestanding bilayer lipid membranes varies in the opposite manner to that of supported membranes.

Fund: The project was supported by the Natural Science Foundation of Fujian Province, China (2012J01054), National Natural Science Foundation of China (21021002), and Fundamental Research Funds for the Central Universities, China (2012121026).